<template>
    <div>
        <router-link to="/" tag="div" class="header-abs" v-show="showAbs">
            <span class="iconfont header-abs-back">&#xe624;</span>
        </router-link>
        <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
            景点详情
            <router-link to="/">
                <div class="iconfont header-fixed-back">&#xe624;</div>
            </router-link>
        </div>
    </div>
</template>

<script>
export default {
    name: 'DetailHeader',
    data(){
        return{
            showAbs: true,
            opacityStyle: {
                opacity: 0
            }
        }
    },
    methods: {
        handleScroll(){
            const top = document.documentElement.scrollTop || window.pageYOffset || document.body.scrollTop
            if(top > 60){
                let opacity = top/140
                opacity = opacity > 1 ? 1 : opacity
                this.opacityStyle = {
                    opacity: opacity
                }
                this.showAbs = false
            }
            else{
                this.showAbs = true
            }
        }
    },
    activated(){  //keepalive使用时，组件显示时执行 -绑定window事件
        window.addEventListener('scroll',this.handleScroll)
    },
    deactivated(){  //keepalive使用时，组件隐藏时执行 --解绑window事件
        window.removeEventListener('scroll',this.handleScroll)
    }
}
</script>

<style lang="stylus" scoped>
    @import '~styles/varibles.styl'

    .header-abs
        position absolute
        left .2rem
        top .2rem
        width .8rem
        height .8rem
        line-height .8rem
        text-align center
        border-radius .4rem
        background rgba(0,0,0,.8)
        .header-abs-back
            color #ffffff
            font-size .4rem
    .header-fixed
        position fixed
        top 0
        left 0
        right 0
        height $headerHeight
        line-height  $headerHeight
        text-align center
        font-size .32rem
        color #fff
        background $bgColor
        z-index 2
        .header-fixed-back
            position absolute
            top 0
            left 0
            width .64rem
            text-align center
            font-size .4rem
            color #fff
</style>

